Method of gap-filling using amplitude modulation radiofrequency power and apparatus for the same

ABSTRACT

A method of filling a gap on a substrate comprises disposing the substrate, on which the gap is formed, on a susceptor in a chamber; applying a source power to the chamber to generate plasmas into the chamber; supplying a process gas into the chamber; filling a thin film into a gap by applying a first bias power to the susceptor, an amplitude of the first bias power being periodically modulated; stopping supply of the process gas and cutting off the first bias power; and extinguish the plasmas in the chamber.

The present invention claims the benefit of Korean Patent ApplicationsNo. 2006-0042031 filed in Korea on May 10, 2006, which is herebyincorporated by references.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of gap-filling used forfabricating a semiconductor device, and more particularly, to a gap-fillmethod using an amplitude modulation radiofrequency (RF) power and anapparatus for the same.

2. Discussion of the Related Art

There are many trenches and holes (or gaps) to be filled up when formingseparating layer between elements, an inter metal dielectric (IMD) layerand an interlayer dielectric (ILD) layer in a fabricating process of asemiconductor device. Recently, since a density of semiconductor deviceincreases and a width of a metal line and a distance between devicesdecrease, widths of the trenches and gaps decrease. As a result, thereis requirement to be improved in a gap-fill process.

There are many methods for gap-filling. Among these gap-filling methods,since high aspect ratio is required, a high density plasma chemicalvapor deposition (HDPCVD) method has been widely because of excellentgap-fill characteristics. In the HDP CVD method, the gaps are filled upusing high density plasma.

FIG. 1 is a schematic cross-sectional view showing a conventional highdensity plasma chemical vapor deposition (HDPCVD) apparatus. As shown inFIG. 1, a conventional HDPCVD apparatus 10 includes a chamber 11, asusceptor 12, a gas injector 13, a RF antenna 14, a source RF powersupply 15, a bias RF power supply 17 and a direct current (DC) powersupply 20. The chamber 11 has an inner reactive space. An insulatingplate 21, which isolates an inner space of the chamber 110 from an outerspace, is disposed on an upper wall of the chamber 11. The susceptor 12is disposed in the chamber 11. A substrate “w” is loaded on thesusceptor 12. The gas injector 13 is disposed on opposite side walls ofthe chamber 11 and around the susceptor 12. The gas is injected into thechamber 11 through the gas injector 13. The RF antenna 14 is disposedover the chamber 11 and functions as a plasma injecting source. The RFantenna 14 is connected to the source RF power supply 15. The bias RFpower supply 17, which controls an energy density of ion supplied ontothe substrate “w”, is connected to the susceptor 12. Generally, a powerfrequency of the source RF power supply 15 may be one of 400 KHz, 2 MHz,13.56 MHz and more than 27.12 MHz. A power frequency of the bias RFpower supply 17 may be one of 13.56 MHz or less than 2 MHz. A sourcematching circuit 16 and a bias matching circuit 18 are respectivelyconnected to the source RF power supply 15 and the bias RF power supply17 to matches impedances. In addition, a direct current (DC) electrode19 is formed in the susceptor 12 to be closet the substrate to thesubstrate 12 using a static electricity. The DC electrode 19 is formedof a metallic material such as tungsten (W). The DC electrode 19 isconnected to a DC power supply 20.

A gap-filling process in the above-mentioned HDPCVD device 10 isexplained.

A substrate “w” is loaded on a susceptor 12, and inert gases areinjected into the chamber 11. And then, plasma is supplied into thechamber 11 by applying a source voltage from the source RF power supply15 to the RF antenna 14. At this time, a reactant gas, such as silane(SiH₄) and oxygen (O₂), is injected onto the substrate “w” on thesusceptor 12, and the bias RF power supply 17 is turned on. The reactantgas, such as silane (SiH₄) and oxygen (O₂), is changed into ions andactive gases by colliding with electrons to depositing and etching asurface of the substrate “w”. The ions and electrons are accelerated bythe bias RF power supply 17. Generally, since a depositing rate isgreater than an etching rate, the reactant gas is deposited on thesubstrate “w”. The active gases contribute to the depositing, while theions and electrons contribute to the etching.

When a depositing process is performed without an etching process, thereare voids in the gap. FIGS. 2A to 2C are cross-sectional views showing avoid formed during a gap-filling process according to the related art.As shown in FIG. 2A, a plurality of gaps “T” are formed on the substrate“w”. As shown in FIG. 2B, A material is deposited on the substrate “w”and into the plurality of gaps “T”, and an inlet of the gap is muchnarrow than other portions of the gap. As a material is deposited, theinlet of the gap is choked before the inner space of the gap isperfectly filled with the material, thereby forming a void in the innerspace of the gap. It may be referred to as an overhang phenomenon. Otherportions of the gap except for the void are filled up by the material.To avoid the overhang phenomenon, the material deposited on thesubstrate “w” is etched by accelerated ions during deposition of thematerial.

However, since a width of metal line and a distance of devices, whichare referred to as a critical dimension, decrease more and more, theabove method, in which a material is deposited and etched at the sametime to prevent the overhang phenomenon, has it's limits to prevent thevoid. It is because that a by-product from etching process is depositedagain in the gap, not exhausted, as the critical dimension decreases. Itmakes the inlet of the gap narrowed. Since pressure around the inlet ofthe gap is higher than that of other portions of the gap due to ions andelectrons diffused to the substrate, an etched material can not beexhausted.

As a result, when the critical dimension is less than 100 nm, there aresome voids in the gap even if the material on the inlet of the gap isetched.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method ofgap-filling and an apparatus for the same that substantially obviatesone or more of the problems due to limitations and disadvantages of therelated art.

An object of the present invention is to provide a method of gap-fillingbeing capable of filling a gap without voids and an apparatus for thesame.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a method offilling a gap on a substrate comprises disposing the substrate, on whichthe gap is formed, on a susceptor in a chamber; applying a source powerto the chamber to generate plasmas into the chamber; supplying a processgas into the chamber; filling a thin film into a gap by applying a firstbias power to the susceptor, an amplitude of the first bias power beingperiodically modulated; stopping supply of the process gas and cuttingoff the first bias power; and extinguish the plasmas in the chamber.

In another aspect, a method of filling a gap on a substrate disposed ona suscepotor comprises forming plasmas over the substrate; supplying aprocess gas over the substrate; applying a first power to the susceptorto deposit the process gas onto the substrate and fill a thin film intothe gap, the first power being modulated to have different amplitudes;stopping supply of the process gas and cutting off the first power; andextinguishing the plasmas.

In another aspect, a method of filling a gap on a substrate, the methodincluding supplying a source power into a chamber to generate plasmas,injecting a process gas into the chamber, and supplying a bias power toa susceptor, on which the substrate is disposed, in the chamber todeposit the process gas onto the substrate and fill the gap comprisesexecuting a first step of increasing acceleration of ion of the processgas diffused onto the substrate; and executing a second step ofdecreasing acceleration of ion of the process gas diffused onto thesubstrate, wherein the first step and the second step are periodicallyrepeated.

In another aspect, an apparatus for filling a gap on a substratecomprises a chamber having an inner space; a susceptor, on which thesubstrate is disposed, in the inner space of the chamber; a gas injectorsupplying a processing gas into the chamber; a plasma generating unitdisposed at an upper side of the chamber; a source RF power supplyapplying a source power to the plasma generating unit; a bias RF powersupply supplying a bias power to the susceptor; and an amplitudemodulation unit between the bias RF power supply and the susceptor,wherein the bias power is modulated by the amplitude modulating unit tohave different amplitudes.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a schematic cross-sectional view showing a conventional highdensity plasma chemical vapor deposition (HDPCVD) apparatus.

FIGS. 2A to 2C are cross-sectional views showing a void formed during agap-filling process according to the related art.

FIG. 3 is a schematic cross-sectional view showing a high density plasmachemical vapor deposition (HDPCVD) apparatus according to a firstembodiment of the present invention,

FIG. 4 is a schematic view showing an amplitude modulation unit in thepresent invention.

FIG. 5 shows a waveform of an modulated power generating by an amplitudemodulating unit.

FIGS. 6A and 6B show waveforms when a modulation index has a value of0.5 and 1, respectively.

FIG. 7 is a flow chart showing a method of gap-filling.

FIG. 8 is a schematic cross-sectional view showing a high density plasmachemical vapor deposition (HDPCVD) apparatus according to a secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings.

FIG. 3 is a schematic cross-sectional view showing a high density plasmachemical vapor deposition (HDPCVD) apparatus according to a firstembodiment of the present invention. As shown in FIG. 3, a HDPCVDapparatus 100 includes a chamber 110, a susceptor 120, a gas injector130, a radiofrequency (RF) antenna 140, a source RF power supply 150, abias RF power supply 170, a direct current (DC) power supply 200 and anamplitude modulation unit 300. The chamber 110 has an inner reactivespace. An insulating plate 210, which isolates an inner space of thechamber 110 from an outer space, is disposed on an upper wall of thechamber 110. The susceptor 120 is disposed in the chamber 110. Asubstrate “w” is loaded on the susceptor 120. The gas injector 130 isdisposed on opposite side walls of the chamber 110 and around thesusceptor 120. The gas is injected into the chamber 110 through the gasinjector 130. The RF antenna 140 is disposed over the chamber 110 andfunctions as a plasma injecting source. The RF antenna 140 is connectedto the source RF power supply 150. The bias RF power supply 170, whichcontrols an energy density of ion supplied onto the substrate “w”, isconnected to the susceptor 120. A source matching circuit 160 and a biasmatching circuit 180 are respectively connected to the source RF powersupply 150 and the bias RF power supply 170 to matches impedances. Inaddition, a direct current (DC) electrode 190 is formed in the susceptor120 to be closet the substrate to the substrate 120 using a staticelectricity. The DC electrode 190 is formed of a metallic material suchas tungsten (W). The DC electrode 190 is connected to a DC power supply200. The amplitude modulation unit 300 is connected to the bias matchingcircuit 180 and the bias RF power supply 170. A power from the bias RFpower supply 170 is modulated by the amplitude modulation unit 300 tohave various amplitudes periodically. Accelerations of the ions diffusedonto the substrate “w” are periodically changed depending on theamplitudes of the modulated powers. Namely, as a voltage of the bias RFpower supply 170 increases, accelerations of the ions also increase. Inother hands, when a voltage of the bias RF power supply 170 decreases,accelerations of the ions also decrease. The accelerations of the ionsare proportional to the magnitude of the voltage of the bias RF powersupply 170. Moreover, an amount of ions diffused onto the substrate isproportional to the acceleration of the ions. Deposition and etching aremore active when an amount of ions diffused onto the substrate “w”increases. Additionally, a by-product is much generated as an etching ismore active. With a high acceleration of ion, ions diffused on an innerspace of the gap increase and by-products on the inlet of the gap alsoincrease. With a low acceleration of ion, both ions diffused on an innerspace of the gap and by-products on the inlet decrease. Accordingly,when acceleration of ions decreases and ions diffused on the substrate“w” decrease, the by-products can be much exhausted to outer space ofthe gap. Since by-products are actively exhausted and are not depositedagain on the substrate “w”, a deposition rate on the inlet portion ofthe gap decreases such that there are increased time to fill up theinner space of the gap. As a result, a void is not generated in the gap.Namely, the overhang phenomenon can be solved and there is no void inthe gap with a low acceleration of ion.

FIG. 4 shows an amplitude modulation unit of an apparatus forgap-filling according to the present invention. As shown in FIG. 4, theamplitude modulation unit 300 is connected to both a bias RF powersupply 170 and the bias matching circuit 180. The amplitude modulationunit 300 includes a local oscillator 310, a power mixer 320, a firstamplifier 330, a second amplifier 340 and a phase lock loop (PLL) 350.The local oscillator 310 generates a power having a frequency differentfrom that of the bias RF power supply 170. The power from the localoscillator 310 has a frequency less than that of RF power supply 170.The power mixer 320 receives and mixes powers from the bias RF powersupply 170 and the local oscillator 310. The first amplifier isconnected to the power mixer 320 and receives the mixed power.

Assumes that a power function of the bias RF power supply 170 is“cos(ω_(c))t”, a power function of the local oscillator 310 is“1+cos(ω_(m))t”. In this case, a power function of the power mixer 320is given by:

(1+cos(ω_(m))t)cos(ω_(c))t

Wherein “ω_(c)” and “ω_(m)” are angular frequencies of powers from thebias RF power supply 170 and the local oscillator 310′, respectively.And “m” is a modulation index.

The power of the power mixer 320 has a waveform shown in FIG. 5. Thewaveform in FIG. 5 has an envelop with a maximum amplitude “A” and aminimum amplitude “B”. In this case, the modulation index “m” is givenby:

m=(A−B)/(A+B)

Since the power function of the power mixer 320 is rewritten by:

(1+cos(ω_(m))t)cos(ω_(c))t=cos(ω_(c))t+(m/2)cos(ω_(c)+ω_(m))t+(m/2)cos(ω_(c)−ω_(m))t

Accordingly, the power function of the power mixer 320 includes variousfrequencies, such as “ω_(c)”, “(ω_(c)+ω_(m))” and “(ω_(c)−ω_(m))”.

The bias RF power supply 170 has a frequency with a range between 100KHz and 30 MHz. In more particular, the bias RF power supply 170 has afrequency of one of 2 MHz, 13.56 MHz and 27.12 MHz. The local oscillator310 has a frequency with a range between 10 Hz and 2 MHz. The bias RFpower supply 170 and the local oscillator 310 have frequencies with arelation by:

ω_(c)≧10ω_(m)

On the other hand, a magnitude of the source RF power supply 150 isvarious depending on a size of the substrate “w”. However, a power ofthe source RF power supply 150 having a value less than 20 W/cm² isapplied. If possible, the power of the source RF power supply 150 havinga value greater than 20 W/cm² may be applied depending on requirement.

FIG. 5 is a graph plotting time versus voltage of power from a powermixer when the modulation index “m” is 0.5. An amplitude of power fromthe bias RF power supply 170 is modulated by the power mixer 320 to bevarious depending on time. The power from the power mixer 320 has threefrequencies of “ω_(c)”, “(ω_(c)+ω_(m))” and “(ω_(c)−ω_(m))”, and has amaximum power at a range of the angular frequency “ω_(c)” of the bias RFpower supply 170.

Since the modulation index “m” is given by:

m=(A−B)/(A+B),

a waveform of the power is various depending on a value of themodulation index “m”. For example, if the modulation index “m” has avalue of 1, the minimum amplitude “B” of the envelope becomes zero suchthat the power is not transferred. And if the modulation index “m” has avalue of 0.5, the maximum amplitude “A” of the envelope is three timesas much as the minimum amplitude “B” of the envelope. (A=3B)

FIGS. 6A and 6B show waveforms when a modulation index has a value of0.5 and 1, respectively. When the modulation index “m” has a relativelow value, there are fluctuations of amplitude in the powers. However,there is no disconnection in the power. On the other hand, when themodulation index “m” has a relative high value, the minimum amplitude“B” (of FIG. 5) becomes a substantially zero such that the power is nottransferred. Namely, when the modulation index “m” has a relative highvalue, there are much fluctuations of amplitude in the powers.Accordingly, in the present invention, the modulation index “m” has avalue greater than 0.5 to have much fluctuations of the amplitude andmuch variance in acceleration of the ions.

Hereinafter, a method of gap-filling in a high density plasma chemicalvapor disposition (HDPCVD) device according to the present inventionwith reference to FIGS. 3 and 7. FIG. 7 is a flow chart showing a methodof gap-filling.

First, in a first step “ST110”, a substrate “w”, on which a plurality ofgap is formed, is loaded on a susceptor 120 in a chamber 110. Next, in asecond step “ST120”, an inert gas, such as argon (Ar), helium (He) andhydrogen (H2), is inject into the chamber 110 to stabilize the innerspace of the chamber 110. Next, in a third step “ST130”, when the innerspace of the chamber 110 is maintained to be constant, a source RF powersupply 150 is turned on to generate plasma into the inner space of thechamber 110. A current of the source RF power supply 150 has a valuewith a range between hundreds KHz and dozens MHz. The current of thesource RF power supply 150 may have a value one of 13.56 MHz and 27.12MHz. A power of the source RF power supply 150 is various depending onprocess conditions. The power of the source RF power supply 150 may havea value less than 20 W/cm2.

Next, in a fourth step “ST140”, when plasma is stabilized, process gasesare injected into the chamber 110 through the gas injector 130, and thebias RF power supply 170 is turned on to apply a power having modulatedamplitudes into the susceptor 120. A kind of the process gases arevarious depending on what being deposited onto the substrate “w”. Forexample, when a silicon oxide layer is deposited onto the substrate “w”,a gas including silicon (Si), e.g., silane (SiH₄) gas, oxygen (O₂) gasand ozone (O₃) gas are used for the process gases. During the processgases being injected, the inert gas may be injected or not. Moreover,during the process gases being injected, pressure in the inner space ofthe chamber 10 may be maintained in pressure less than several mTorr.The inner space of the chamber 110 may have pressure less than lmTorrdepending requirement. As mentioned above, to modulate amplitude ofpowers from the bias RF power supply 170, a local oscillator 310 of theamplitude modulation unit 300 generates a power having a frequency witha range between 10 Hz and 2 MHz. In this case, an angular frequency“ω_(c)” of the bias RF power supply 170 and an angular frequency “ω_(m)”of the local oscillator 310 has a relation give by:

ω_(c)≧10 ω_(m)

In the fourth step “ST140”, when a power from the bias RF power supply170 is applied into the susceptor 120, a rear side of the substrate “w”is cooled by using helium gas depending on process temperature.

Next, in a fifth step “ST150”, a gap-filling process is performed tofill a thin film into the gap without voids. Namely, silane gas andoxygen gas are activated to be ions and activating gases and aredeposited onto and etches surface of the substrate “w” at the same time.In the present invention, since a power of the bias RF power supply 170is modulated by the amplitude modulation unit 300 and then applied intothe susceptor 120, accelerations of ions are fluctuated depending onamplitudes of the power. Accordingly, when the amplitude is high, amountof ions diffused onto the substrate “w” increases such that thedepositing and etching are activated. On the other hand, when theamplitude is low, amount of ions diffused onto the substrate “w”decreases such that a depositing rate at a inlet portion of a gapdecreases. It is because by-products are easily exhausted into an outerspace of the gap, as mentioned above. Accordingly, the gap can be filledup by a material without a void.

Next, in sixth and seventh steps “ST160” and “ST170”, after finishingthe gap-filling process, supply of the process gases is interrupted, thebias RF power supply 170 and the source RF power supply 150 are turnedoff. As a result, plasma disappears. Depending on requirement, the inertgas may be continuously supplied.

If the inert gas is continuously supplied, supply of the inert gas isinterrupted in an eighth step “ST180”. And then, in a ninth step“ST190”, the substrate “w” is carried out.

On the other hand, in the fourth step “ST140”, it is not required thatthe power having modulated amplitudes are applied during a whole processtime. The power having modulated amplitudes may be applied during ainitial process time, and a power without amplitude modulating may beapplied during later process time. Namely, the depositing processincludes a step of modulating the power and a step of non-modulating thepower. When the step of modulating the power is changed into the step ofnon-modulating the power, a modulating index becomes smaller stepwise.The smaller the modulating index becomes, the smaller difference betweena maximum amplitude of a modulated power from the power mixer and aminimum amplitude of the modulated power from the power mixer becomes.

On the other hand, the depositing process divided into three steps of aninitial non-modulating step, a modulating step and a laternon-modulating step.

In an initial stage of the depositing process, since the gap is filledup without voids and the aspect ratio becomes large, a power is notrequired to be modulated. When the gap is partially filled up, then, themodulating step is performed. And after the gap is filled up, the laternon-modulating step is performed. Period of the initial non-modulatingstep is determined depending on a shape of the gap. When the initialnon-modulating step is changed into the modulating step, a modulationindex becomes larger stepwise. The larger the modulation index becomes,the larger difference between a maximum amplitude of a modulated powerfrom the power mixer and a minimum amplitude of the modulated power fromthe power mixer becomes. And when the modulating step is changed intothe later non-modulating step, a modulating index becomes smallerstepwise.

To obtain the above-mentioned process, a bias RF power supply 170 isconnected to an amplitude modulation unit 300 via a switching unit 400,as shown in FIG. 8. FIG. 8 is a schematic cross-sectional view showing ahigh density plasma chemical vapor deposition (HDPCVD) apparatusaccording to a second embodiment of the present invention.

When the switching unit 400 is turned on, the bias RF power 170 isconnected to the amplitude modulation unit 300 such that a power fromthe bias RF power 170 is modulated by the amplitude modulation unit 300.However, when the switching unit 400 is turned off, the bias RF power170 is disconnected to the bias matching circuit 180 such that a powerfrom the bias RF power 170 is not modulated by the amplitude modulationunit 300. When the switching unit 400 is turned off, the bias RF power170 is directly connected to a bias matching circuit 180.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the apparatus having a highgas conductance without departing from the spirit or scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

1. A method of filling a gap on a substrate, comprising: disposing thesubstrate, on which the gap is formed, on a susceptor in a chamber;applying a source power to the chamber to generate plasmas into thechamber; supplying a process gas into the chamber; filling a thin filminto a gap by applying a first bias power to the susceptor, an amplitudeof the first bias power being periodically modulated; stopping supply ofthe process gas and cutting off the first bias power; and extinguishingthe plasmas in the chamber.
 2. The method according to claim 1, whereinthe step of applying the first bias power includes mixing first andsecond power having different frequencies from each other to generatethe first bias power.
 3. The method according to claim 2, wherein thefirst power has a frequency with a range of 100 KHz to 30 MHz, and thesecond power has a frequency with a range of 10 Hz to 2 MHz.
 4. Themethod according to claim 2, whereinω_(c)≧10ω_(m), wherein ω_(c) is an angular frequency of the first power,and ω_(m) is an angular frequency of the second power.
 5. The methodaccording to claim 1, whereinm=(A−B)/(A+B)=0.5, wherein m is a modulation index of the first biaspower, A is a maximum amplitude of the first bias power, and B is aminimum amplitude of the first bias power.
 6. The method according toclaim 1, further comprising applying a second bias power to thesusceptor after applying the first bias power, the second bias power isnot modulated to have substantially the same amplitude.
 7. The methodaccording to claim 6, wherein a modulation index of the first bias powerbecomes smaller to perform the step of the applying the second biaspower, whereinm=(A−B)/(A+B), wherein m is a modulation index of the first bias power,A is a maximum amplitude of the first bias power, and B is a minimumamplitude of the first bias power.
 8. The method according to claim 6,further comprising applying a third bias power to the susceptor beforeapplying the first bias power, the third bias power is not modulated tohave substantially the same amplitude.
 9. The method according to claim8, wherein a modulation index of the third bias power becomes larger toperform the step of the applying the first bias power, whereinm=(A−B)/(A+B), wherein m is a modulation index of the third bias power,A is a maximum amplitude of the third bias power, and B is a minimumamplitude of the third bias power.
 10. A method of filling a gap on asubstrate disposed on a suscepotor, comprising: forming plasmas over thesubstrate; supplying a process gas over the substrate; applying a firstpower to the susceptor to deposit the process gas onto the substrate andfill a thin film into the gap, the first power being modulated to havedifferent amplitudes; stopping supply of the process gas and cutting offthe first power; and extinguishing the plasmas.
 11. The method accordingto claim 10, further comprising applying a second power to the susceptorbefore and after applying the first power, wherein the second power isnot modulated to have the same amplitude.
 12. A method of filling a gapon a substrate, the method including supplying a source power into achamber to generate plasmas, injecting a process gas into the chamber,and supplying a bias power to a susceptor, on which the substrate isdisposed, in the chamber to deposit the process gas onto the substrateand fill the gap, comprising: executing a first step of increasingacceleration of ion of the process gas diffused onto the substrate; andexecuting a second step of decreasing acceleration of ion of the processgas diffused onto the substrate, wherein the first step and the secondstep are periodically repeated.
 13. The method according to claim 12,wherein the first step includes increasing an amplitude of the biaspower.
 14. The method according to claim 12, wherein the second stepincludes decreasing an amplitude of the bias power.
 15. An apparatus forfilling a gap on a substrate, comprising: a chamber having an innerspace; a susceptor, on which the substrate is disposed, in the innerspace of the chamber; a gas injector supplying a processing gas into thechamber; a plasma generating unit disposed at an upper side of thechamber; a source RF power supply applying a source power to the plasmagenerating unit; a bias RF power supply supplying a bias power to thesusceptor; and an amplitude modulation unit between the bias RF powersupply and the susceptor, wherein the bias power is modulated by theamplitude modulating unit to have different amplitudes.
 16. Theapparatus according to claim 15, further comprising a switching unitbetween the amplitude modulating unit and the bias RF power supply,wherein the bias power is modulated by the amplitude modulation unitwhen the switching unit is turned on, and the bias power is notmodulated when the switching unit is turned off.
 17. The apparatusaccording to claim 15, wherein the amplitude modulation unit includes; alocal oscillator generating a local power having a different frequencyfrom a frequency of the bias power; and a power mixer mixing the localpower and the bias power to modulate the bias power.
 18. The apparatusaccording to claim 17, wherein the bias power has a frequency with arange of 100 KHz to 30 MHz, and the local power has a frequency with arange of 10 Hz to 2 MHz.
 19. The apparatus according to claim 17,whereinω_(c)≧10 ω_(m), wherein ω_(c) is an angular frequency of the bias power,and ω_(m) is an angular frequency of the local power.
 20. The apparatusaccording to claim 17, whereinm=(A−B)/(A+B)=0.5, wherein m is a modulation index of the modulated biaspower, A is a maximum amplitude of the modulated bias power, and B is aminimum amplitude of the modulated bias power.